P.300Diaphragm imaging in Duchenne muscular dystrophy (DMD)

Abstract

Reliable outcome measures able to demonstrate specific trends of disease progression are essential in this era of clinical trials in DMD. Magnetic resonance imaging (MRI) is increasingly being used to assess muscular degeneration in dystrophic patients. We studied muscle diaphragm through MRI and correlated MRI measurements of diaphragm structure and function with compartmental tidal volumes measured by opto-electronic plethysmography (OEP) and pulmonary function tests. 26 DMD patients and 12 age-matched controls were acquired in breath-hold on a 3T-scanner at full-expiration (EXP) and full-inspiration (INSP), by a multi-point gradient echo Dixon sequence. We measured: 1) cranio-caudal diaphragmatic excursion as the median vertical distance between the EXP and INSP diaphragm surfaces; 2) muscle fatty infiltration as the amount of intramuscular adipose tissue in regions of interest. DMD patients and controls were also acquired during quiet breathing in supine posture by OEP; ribcage and abdominal volume variations were measured and expressed as percentage contribution to tidal volume. Cranio-caudal excursion of the diaphragm correlated positively to abdominal volume variation (r=0.61, p=0.0001) and negatively to rib cage volume variation (r=-0.60, p=0.0002). Diaphragm excursion decreased with decreasing FEV1 %pred (r=0.78, p<0.0001) and FVC %pred (r=0.76, p<0.0001). Fatty infiltration increased with decreasing FEV1 %pred (r=-0.88, p<0.0001) and FVC %pred (r=-0.88, p<0.0001). The progressive structure and function impairment of the diaphragm is highly related to compartmental tidal volumes and to pulmonary function tests.